<!DOCTYPE html>
<title>Tests that layout is updated on position-anchor value changes</title>
<link rel="help" href="https://drafts4.csswg.org/css-anchor-position-1/#position-anchor">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
#target {
  position: fixed;
  width: 100px;
  height: 100px;
  background: lime;
  top: anchor(top);
  left: anchor(right);
  position-anchor: --a;
}

#target.after {
  position-anchor: --b;
}

#anchor1, #anchor2 {
  width: 100px;
  height: 100px;
  background: orange;
}

#anchor1 {
  anchor-name: --a;
}

#anchor2 {
  margin-left: 100px;
  anchor-name: --b;
}

body {
  margin: 0;
}
</style>

<div id="anchor1"></div>
<div id="anchor2"></div>
<div id="target"></div>

<script>
test(() => {
  document.body.offsetLeft; // Force layout
  target.classList.add('after');
  // #target should be anchored to #anchor2 now
  assert_equals(target.offsetLeft, 200);
  assert_equals(target.offsetTop, 100);
}, 'Layout is updated on `position-anchor` changes');
</script>
